Alex Chang, MD, MS is a Clinical Investigator in the Department of Nephrology at Geisinger Health System. He is applying for a Mentored Patient-Oriented Research Career Development Award in order to develop the requisite skills and mentored research experience to become an independent physician scientist with a focus on prevention/slowing the progression of chronic kidney disease through control of obesity and improvements in diet. This research proposal includes a 5-year plan that includes mentorship by Dr. Lawrence Appel, MD, MPH, Dr. David Carey, PhD, and Dr. Morgan Grams, MD, PhD; completion of courses in epidemiology, biostatistics, and clinical trials; and retrospective and prospective studies examining the effect of bariatric surgery on kidney function. The specific aims of the research agenda are to: 1) compare long-term kidney function trajectories between bariatric surgery patients and morbidly obese controls using the current clinical standard, eGFR based on serum creatinine (N=6200); 2) Assess associations between filtration markers (creatinine, cystatin C, BTP, and B2M) and directly measured GFR in a prospective cohort of patients undergoing bariatric surgery (n=40); 3) estimate long-term kidney function trajectories by multiple markers and compare trajectories between bariatric surgery patients and morbidly obese controls in a subsample with repeat biobanked specimens (N=400). Successful completion of this research will fill critical knowledge gaps in understanding the long-term effect of weight loss on kidney function while examining whether alternative filtration markers can improve estimation of kidney function in patients with morbid obesity. Further, completion of this research will fulfill the candidate's short-term career goals of developing a strong knowledge base in study design, longitudinal data analysis, multilevel modeling, and recruitment/retention of participants in long-term studies. This K award will also accelerate the candidate's long term objectives of conducting independent investigations on the effects of lifestyle modification and obesity prevention/control on progression of kidney disease, leveraging opportunities for comparative effectiveness research in a large, integrated, rural healthcare system.